Supramolecular Organization of Apolipoprotein-A-I-Derived Peptides within Disc-like Arrangements

Abstract

Apolipoprotein A-I is the major protein component of high-density lipoproteins and fulfils important functions in lipid metabolism. Its structure consists of a chain of tandem domains of amphipathic helices. Using this protein as a template membrane scaffolding protein, class A amphipathic helical peptides were designed to support the amphipathic helix theory and later as therapeutic tools in biomedicine. Here, we investigated the lipid interactions of two apolipoprotein-A-I-derived class A amphipathic peptides, 14A (Ac-DYLKA FYDKL KEAF-NH 2) and 18A (Ac-DWLKA FYDKV AEKLK EAF-NH 2), including the disc-like supramolecular structures they form with phospholipids. Thus, the topologies of 14A and 18A in phospholipid bilayers have been determined by oriented solid-state NMR spectroscopy. Whereas at a peptide-to-lipid ratio of 2 mol% the peptides align parallel to the bilayer surface, at 7.5 mol% disc-like structures are formed that spontaneously orient in the magnetic field of the NMR spectrometer. From a comprehensive data set of four 15 Nor 2 H-labeled positions of 14A, a tilt angle, which deviates from perfectly in-planar by 14 , and a model for the peptidic rim structure have been obtained. The tilt and helical pitch angles are well suited to cover the hydrophobic chain region of the bilayer when two peptide helices form a head-to-tail dimer. Thus, the detailed topology found in this work agrees with the peptides forming the rim of nanodiscs in a double belt arrangement.

The Reversible Non-covalent Aggregation Into Fibers of PGLa and Magainin 2 Preserves Their Antimicrobial Activity and Synergism

“…These biophysical studies show that magainin 2 adopts very stable alignments parallel to the membrane surface under all conditions tested so far (Bechinger, 2011;Salnikov and Bechinger, 2011;Strandberg et al, 2013), a feature also observed for many other related peptides (Porcelli et al, 2013;Resende et al, 2014;Perrin et al, 2015;Salnikov et al, 2018). In contrast to magainin 2, the membrane topological alignment of PGLa is modulated by the detailed composition of the phospholipid membrane, its peptide-to-lipid ratio, the hydration level or the presence of magainin 2 (Tremouilhac et al, 2006;Salnikov and Bechinger, 2011;Strandberg et al, 2013).…”

The Mechanisms of Action of Cationic Antimicrobial Peptides Refined by Novel Concepts from Biophysical Investigations

“…When membranes are uniaxially oriented relative to the magnetic field of the NMR spectrometer, a unique molecular alignment is retained, spectral resolution is recovered, and the resulting anisotropic chemical shifts and dipolar and quadrupolar interactions provide valuable information about the orientation of bonds, protein domains, and polypeptides as a whole. Thus, the corresponding spectra can be used to analyze the structure, dynamics, and topology of membrane-associated polypeptides (Das et al 2015;Gopinath et al 2015;Itkin et al 2017;Salnikov et al 2018).…”

“…Whereas the 15 N chemical shift alone provides an approximate tilt angle of helical domains (Bechinger and Sizun 2003), the combination with 2 H solid-state NMR spectra from methyldeuterated alanines results in accurate tilt and pitch angle information (Fig. 4.3) Salnikov et al 2018).…”

High-Resolution Structural Studies Elucidate Antiatherogenic and Anti-Inflammatory Properties of Peptides Designed to Mimic Amphipathic α-Helical Domains of Apolipoprotein A-I

“…Thus, the detailed topology found in this work agrees with the peptides forming the rim of nanodiscs in a double-belt arrangement. 25 An important observation is that the head-to-tail orientation of these peptides around the edge of discoidal structure strongly support the interaction of π-electron containing aromatic rings for the stabilization of discoidal structures.…”